1. Field of the Invention
The present invention relates to an ultraviolet ray irradiation apparatus for fixing printed material, which is used while connected to a printed material discharge port of a printing apparatus employing ultraviolet curable ink (also known as UV curable ink) to irradiate an image surface of a printed material with ultraviolet rays, and more particularly to control of a printed material conveyance speed thereof.
2. Description of the Background Art
A stencil printer, for example, has low running costs and is capable of printing at high speed, and is therefore used widely for printing various printed materials, forms, and so on in educational institutions, public offices, organizations, hospitals, and soon. Stencil printers are also used for printing multiple copies of printed materials such as newspaper inserts, real estate publications, and in-house written communications in private enterprises. To ensure that the stencil printer can be operated easily by anybody at any time, a printing ink that does not harden in air is typically employed so that there is no need to clean the printing drum unit every time it is used. This stencil ink permeates the paper so as to give the appearance of being dry, but immediately after printing, the ink on printed material is not yet dry, and if this ink is touched, the printed image is easily spoiled. This has been identified as a serious problem in conventional stencil printing apparatuses, but no proposed measures have been implemented effectively.
A stencil printing apparatus that performs stencil printing using an ultraviolet curable ink and an ultraviolet ray irradiation apparatus for irradiating the printed material of the stencil printing apparatus with ultraviolet rays have been proposed as methods for improving the drying of printed material.
For example, Japanese Utility Model Publication H4-35188 relates to a stencil printing apparatus in which an ultraviolet ray irradiator is provided above a belt conveyor of a paper discharge apparatus. A cylindrical plate cylinder performs a single revolution during engraving in order to discharge a plate, but is stationary at all other times. Hence, at all times other than when the cylindrical plate cylinder position moves by a single revolution during engraving to discharge a plate, a solenoid is electrified and a movable slit plate is positioned in a shielding position shown in the drawings. As a result, ultraviolet rays issued by an ultraviolet lamp are prevented from exiting a lamp house.
Further, Japanese Unexamined Patent Application Publication H5-64878 relates to an ultraviolet fixing apparatus which irradiates a sheet of paper printed by printing means for performing printing using an ultraviolet curable ink with ultraviolet rays, thereby fixing the ink onto the printed paper. The ultraviolet fixing apparatus comprises paper conveyance means for conveying the printed paper separately to the printing means, and ultraviolet ray irradiating means provided above the paper conveyance means for irradiating the printed surface of the paper with ultraviolet rays. The upper portion or side portion of the paper conveyance means is open between the printing means and the ultraviolet ray irradiating means.
In a conventional stencil printing apparatus, an ultraviolet ray irradiation apparatus is disposed in connection with a paper discharge unit, and a printed material discharged therefrom is received and conveyed by the ultraviolet ray irradiation apparatus and then irradiated with ultraviolet rays to cure the image forming ink thereon.
Incidentally, in a printing apparatus, the printing speed may be selected variably, in contrast to an eletrophotographic copier, and therefore an operator sets an arbitrary printing speed. However, if the speed at which an ultraviolet ray irradiation apparatus connected directly to the printed material discharge unit of the printing apparatus receives and conveys the printed material is set at a fixed value, the printing speeds of the two apparatuses do not match, and as a result, a paper jam may occur around the connecting portion. If the paper jam occurs in close proximity to an ultraviolet ray irradiation unit, the ultraviolet ray irradiation time becomes abnormally long, and as a result, the ultraviolet lamp reaches a high temperature, causing excessive degeneration and deformation of the printing paper and a decrease in image quality.
In a printing apparatus, the printed material is delivered by the paper discharge unit and received by the reception unit of the ultraviolet ray irradiation apparatus, and hence it has conventionally been considered desirable to make the discharge speed of the paper discharge unit and the reception/conveyance speed of the ultraviolet ray irradiation apparatus reception unit identical. However, when the two speeds are made identical, the printed material may bend due to slippage caused by a slight speed difference and the effects of the paper type and paper size. Since the connecting portion is small, a bend in the paper is highly likely to create a paper jam.
Furthermore, the printing apparatus main body, to which the ultraviolet ray irradiation apparatus is connected, exists in a plurality of models, and the settable printing speeds and discharge speeds thereof may differ from each other. Hence, a technique for performing optimal control of an operation of the ultraviolet ray irradiation apparatus in accordance with this plurality of models is required.